streaming: Unify codec checking
streaming: Unify codec checking

Avoid copy-pasting to add a new codec

Acked-by: Victor Toso <39b7599ff73bbf5db531748ba5250f21fa7120ff@redhat.com>

fgouget/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk